Effects Of Corrosion On Shear Strength Of Cu/Sn-9zn/Cu Lap Joints In 3.5 Wt. % Nacl Solution
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Date
2013-09
Authors
Affendy, Muhammad Ghaddafy
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
From all the lead (Pb)-free solders made available, the Sn-9Zn solder has promising potentials to be applied in the electrical and electronics industries. Its melting point which is closely similar to Pb-based solders and excellent mechanical strength are requisite qualities to form solder joints in devices. However, the portability of these devices has led to corrosion threats upon the solder joints which may cause adverse effects on its performances. Thus, this research focused on the effects of corrosion on shear strength of Cu/Sn-9Zn/Cu lap joints in 3.5 wt. % NaCl solution. A crosshead speed value of 2.0 mm/min was implemented throughout the strength evaluation. From the shear strength results, the ultimate shear strength (USS) of Cu/Sn-9Zn/Cu lap joints decreased with increasing immersion time. Moreover, the strain at USS greatly reduced as well with increasing immersion time. Corrosion process which occurred during the immersion is mainly responsible to the decrease of shear strength. Pits formed as a result from the corrosion reactions, acted as stress concentration points. With increasing immersion time, these pits enlarged and coalesced with each other to form deep and long cracks on the Sn-9Zn solder surface. Hence, the solder joints are weakened and susceptible to failure. Furthermore, the presence of corrosion products which are tin (II) chloride (SnCl2) and zinc hydroxide chloride [Zn5(OH)8Cl2.H2O] reinforced the statement that corrosion is the factor to the decrease of shear strength. Fracture analysis of lap joints was performed to determine the failure mechanisms.
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Keywords
Corrosion On Shear Strength , Cu/Sn-9zn/Cu Lap Joints